U.S. President Barack Obama is telling China it needs to adopt a more responsible role on the world stage and adhere to international norms.

Before heading to the G-20 summit in China, Obama told CNN in an interview broadcast Sunday that Beijing needs to show restraint in its relations with smaller countries, especially as it deals with territorial disputes in the South China Sea.

The American leader said that "with increasing power comes increasing responsibilities." Obama said the U.S. has urged China to accept international rules that build a strong world-wide order.

South China Sea

China, which is a signatory to the U.N. Convention on the Law of the Sea, recently lost an arbitration dispute at a court in the Hague over the South China Sea, but rejected the ruling. The court ruled China had violated Manila's sovereign rights by interfering with Philippine fishing and oil exploration activities in the area.

South China Sea Territorial Claims

"If you sign a treaty that calls for international arbitration around maritime issues, the fact that you're bigger than the Philippines or Vietnam or other countries... is not a reason for you to go around and flex your muscles," Obama said. "You've got to abide by international law."

Obama said that where the U.S. has seen China "violating international rules and norms, as we have seen in some cases in the South China Sea or in some of their behavior when it comes to economic policy, we've been very firm. And we've indicated to them that there will be consequences."

Trade issues

He said China cannot expect to "pursue mercantilist policies that just advantage" itself now that China has become a more affluent, middle-income country. "Even though you still have a lot of poor people, you know, you can't just export problems. You've got to have fair trade and not just free trade. You have to open up your markets if you expect other people to open up their markets."

Containers are seen at a port in Lianyungang, Jiangsu Province, China, April 13, 2016.

Obama added, "Part of what I've tried to communicate to President Xi [Jinping] is that the United States arrives at its power, in part, by restraining itself. You know, when we bind ourselves to a bunch of international norms and rules it's not because we have to, it's because we recognize that over the long term, building a strong international order is in our interests."